Reciprocating blade lawn mower



Oct. 24, 1950 G. s. FRAMBES 2,526,814

RECIPRQCATING BLADE LAWN MowER Filed May 9, 1947 v2 Sheets-Sheet 1 wuc/Mm. 6: Sfar Hwmbes Oct. 24, 1950 G, s. FRAMBES 2,526,814

RECIPROCATING BLADE LAWN MOWER Filed May 9, 194'? 2 Sheets-Sheet 2 Patented Oct. 24, 1950 UNITED STATES PATgNT lPrice RECIPROCATING BLADE LAWN MOWER Gordon Stark Frambes, Columbus, Ohio Application May 9, 1947, Serial No. 746,981

4 Claims.

My invention relates to lawn mowers, and more particularly to lawn mowers of the type employing transversely reciprocable cutting blades.

In the past, many lawn mowers of this type have been employed, but in most instances have been subject to various objections, due largely to mechanical inefficiency, .structural complexity, and diiiiculties in operation and manufacture. Foremost among the difliculties encountered with lawn mowers of this type, was the frictional drag and unevenness ambient to the driving mechanism employed to effect the reciprocating movement of the associated cutter blade, it being understood, that in such types it is necessaryfto obtain a relatively high speed movement ofthe cutting blade in order to efliciently cut the grass of a lawn or eld. Also, in the operation of such lawn mowers, the cutting blades were oftentimes damaged or broken by the entrance of a stone or stick within the blades, and such damage normally resulted in the necessity of replacing'relatively expensive and complicated parts.

It follows therefore, that the primary object of my invention is to generally improve upon lawn mowers of this type by providing mechanically lefficient and structurally simple driving means for imparting the necessary reciprocating movement to the associated cutter blade with a minimum of frictional drag, and to eliminate unevenness encountered by such movement.

It is another object of my invention to provide a lawn mower of the reciprocating-blade type in which the various component parts may be quickly and easily assembled or disassembled for cleaning, repair or replacement; and which employs relatively inexpensive cuttingblades which may be easily replaced'or sharpened as the occasion arises.

For a further and more detailed understanding of my invention and the Various objects and advantages gained thereby', reference is made to the following description and the appended drawings wherein: I'

Fig. l is a top plan view of a lawn mower formed in accordance with this invention;

Fig. 2 is a vertical sectional view taken along the line 2-2 of Fig. l; e

Fig. 3 is a similar view taken along the line 3-3 of Fig. 1;

Fig. 4 is a top plan view of a modified form of lawn mower formed in accordance with this invention;

Fig. 5 is a vertical sectional View taken along the line 5-5 of Fig. 4

2 Y y Fig. 6 is a vertical sectional view-taken along the line 6-6 vof Fig. 4.

Referring now to the drawings, and more particularly to Figs. l through 3 thereof, the lawn mower illustrated therein comprises va frame, generally indicated by thev numeral IIJ andincluding a pair of transversely spaced circular side plates I I and I2 respectively. Secured to the in.

dividual side plates by means of fastening bolts I3, is a rearwardly and diagonally extending 'fork I4, which receives, as at I5, the` inner end `of a steering tongue i5 which is provided atits upper end in the usual manner with a cross-bar handle I'I. The side plates of the frame are joinedat their rearward ends by means of a cross bar. I8 which serves to rigidly maintain the side plates in their spacedcondition. Support is afforded the forward end of the frame by meansofa transversely disposed plate I 9 which is positioned in a forwardly projecting manner with respect to the side plates II and I2. Positioned at either side of the frame in transverse alignment, and rotatably secured to each of the side plates, are ground wheels 20, each of which is formed upon its outer peripheral surface with friction lugs 2|, and in the normal manner upon its inner surface with a band gear or gear teeth 22. Rotatably carried within the frame I0, is a transversely extending shaft 23 which is provided at its outer ends with gears 24 positioned in meshing engagement with the. band gears formed upon the inner surface of the ground wheels 2U, and which upon rotation of the ground wheels, serve to impart a consequent rotation to the shaft 23,. e, Detachably secured to the forwardly extend? ing cross plate I9 of the frame and extending yfor-'- wardly therefrom, is a stationary cutting blade 25 which comprises a pair of spaced upper and lower plates, 25a and 25h respectively, the latter being formed at their leading edges with a plurality o f pointedteeth 2E. Thel two plates of the blade 25`are held in vertically spaced relationby means of circular collars 2l which extend through open.- ings in the lower plate 25d, and which abut the uppersurface of the cross plate I9 andthe lower surfaceV of the upper plate 25h. 'I he collarsare carried upon a plurality of threaded bolts or. lugs 28 which are held in threaded engagement with the lower cross plate i9 of the frame, and which serve to secure, by means of ,wing nuts 29, the upper and lower plates of the stationary blade. To provide a degree of resiliencyk between the upper and lower plates of the blade, a like nurnber of bow springs 3Q are interposed between .the wing nuts 29 and the upper surface of the upper plate 25D. The bow springs 30 serving to maintain the upper and lower blades in a resiliently separable condition, and to allow resilient parting movement in the event a rock or stick becomes lodged between the two plates. A reciprocable cutter blade 2| is positioned between the upper and lower plates of the stationary blade 25, and is provided with longitudinally disposed slots 32 through which the collars 21 are positioned in order that a limited transverse sliding movement of the reciprocating cutter blade 3| may be obtained. Friction between the reciprocable blade 3l and the stationary blade 25 is limited to the weight of the former acting upon the upper surface of the lower plate 25a, as the upper plate 25h is maintained in xed spaced relation to the lower plate by means of the collar 21. The outer edge of the reciprocable blade 3| is also formed with saw teeth corresponding in dimensions to the teeth 26 disposed at the leading edge of the stationary blade, and as sliding movement obtains within the cutter blade, the teeth thereof will move into and out of registration with the stationary teeth 23, and it will be seen that blades of grass passing through the stationary blade will be severed by the transverse reciprocating action of the cutter blade 3|. The rearward edge of the blade 3| is formed so as to extend rearwardly of the stationary blade 25, and is cut away at its rearward corners to insure ample clearance during reciprocating movement between the blade and the associated frame members.

Reciprocating movement is imparted to the cutter blade 3| through a system of gears driven by. the rotatable shaft 23, which in turn is driven upon rotation of the associated ground wheels 20. The gearing system comprises a bevel gear 33 which is suitably mounted upon the rotatable shaft 23, by means of a pin or key 34. The latter bevel gear, in turn, engages a relatively smaller bevel gear 35 carried at the end of a second rotatable shaft 36 which is disposed within the frame l in perpendicular relation to the rst shaft 23. The second shaft 36 carries at its opposite end a crank arm 31, to which is pivotally connected the inner end of a connecting rod 38. The connecting rod 38 in turn extends diagonally across the forward portion of the lawn mower, and is connected as at 39 to a bracket mounting 40. carried upon the rearward edge of the reciprocating blade 3|. In this manner, it will be seen that upon rotation of the ground wheels 20, reciprocating movement at relatively high speeds is imparted to the reciprocating cutter blade 3|,

in order that the same will move transversely between the stationary blade 25.

Means for elevating the blades and 3| to a desired height with respect to the ground is accomplished by a second pair of ground wheels or rollers 4|, which are rotatably mounted within slots 42 formed within upright portions of the frame |0 which carry the cross plate I9, the rollers being disposed just forwardly of the larger ground wheels 2li and between the latter and the rearward edge of the blade 25. To vary the height of the blades with respect to the ground, adjustment is afforded the rollers 4| by means of tensioning or clamping nuts 43 carried at the inner side of the axle of the rollers, and engageable with the frame at the inner side of the slot 42. The latter provision provides a convenient means for adjusting the height of the cut grass, which may be varied over a relatively wide range from a very close cut to a height approximating two inches. Further, the rollers 4| prevent the blade from digging into the ground, in the event uneven terrain is encountered.

Figs. 4 through 6 of the drawing disclose a modified form of the present invention wherein, the driving mechanism for the associated reciprocating blade 3| is accomplished by means of a pair of segmental pinion gears 44 and 45 respectively. Each of these pinion gears are disposed at the ends of a pair of secondary driven shafts 46 disposed perpendicularly to the shaft 23 driven by the ground wheel 20. Instead of a single bevel gear 33, a pair of bevel gears 4'! are keyed to the shaft 23, and are maintained in meshing engagement with a similar number of bevel gears 48 which serve to impart rotation to the shaft 46. rihe bevel gears 4l are disposed upon the shaft 23 in opposite relation, in order to provide opposite rotation to each of the shafts 46 upon rotation of the ground wheels 28. In this modified form, the rear surface or edge of the cutting blade 3i is provided with a segmental rack gear 49, and as rotation is imparted to the individual segmental pinions 44 and 45, which are disposed in out of phase relation to one another, meshing engagement is obtained between one segment of each gear and one segment of the rack gear 49. Due to the opposite rotation of the two segmental pinion gears, a reciprocating movement is imparted to the rack bar and consequently to the cutting blade 3|. When the segmental pinions are properly positioned upon their respective shafts, a substantially continuous reciprocatingr movement is obtained within the rack gear 49, with one of the pinions sliding the rack gear in one direction, and the other of the pinions returning the same to its original position instantaneously upon release of the first pinion. In this manner, it will be seen that one complete revolution of the pinions will impart a two cycle reciprocating movement to the associated rack gear 49 and its cutter blade, and if the phase or angular disposition of the two pinions is properly adjusted, a substantially constant torque within the rack gear 49 will be obtained.

In both forms of the present invention, protection for the forwardly projecting cutter blades may be had by means of a forwardly projecting guard which, as shown in Fig. 6 of the drawings, may take the formr of a number of forwardly projecting metallic ngers 50, corresponding in number with the number of teeth formed at the forward edge of the stationary blade 25. These ngers may be advantageously secured to the'stationary cross plate I9 of the frame, or may in any suitable manner be connected with one of the plates comprising the stationary blade 25, it being manifest that the fingers are maintained in registration or alignment with the points of the teeth of the blades in order that relatively small stones or sticks may be deected prior to entering the grooved portions of the teeth.

In View of the foregoing, it will be seen that my invention provides both a mechanically eilicient and structurally' simple lawn mower construction utilizing a transversely reciprocating cutter blade. The associated mechanism is characterized by its decreased frictional drag and its smooth and even operation in imparting the necessary reciprocating movement to the associated cutting blade. In a preferred form, the blades of the lawn mower may be easily disassembled by means of the associated wing nuts, for sharpening, repair or replacement and cleaning. Due to. the structural simplicity of lawn mowers formed in accordance with this invention, the cost of manufacture of the same is greatly reduced over previous types.

While I have disclosed what I now deem to be preferred forms of my invention, it will be manifest that various modifications in details of construction and design may be accomplished without departing from the spirit of the invention or the scope of the following claims.

I claim:

1. In a reciprocating blade lawn mower of the type having a frame, ground wheels rotatably carried at either side of the frame, a shaft driven by rotation of the ground wheels, and a flat cutter blade slidably carried on said frame in advance of said ground wheels for reciprocating movement transversely of said frame; a rack gear mounted longitudinally on said blade; a pair of segmental pinion gears rotatably carried in transversely spaced relation on said frame and having teeth alternately engageable with said rack gear to impart reciprocating movement to said cutter blade; and means drivingly connected between said shaft and said pinion gears for imparting rotation to said pinion gears in opposite directions.

2. In a reciprocating blade lawn mower of the type provided with a frame, ground wheels rotatably carried at either side of said frame, a shaft driven by rotation of said ground wheels and extending transversely across said frame, and a cutter blade carried in advance of said ground wheels and arranged for transverse reciprocating movement with respect to said frame; a rack gear carried by said blade longi- Jpudinally thereof; a plurality of oppositely rotating segmental pinion gears journalled on said frame for rotation in a plane perpendicular to the plane of movement of said cutter blade and having gear teeth thereon alternately engageable with said rack gear to impart reciprocating movement to said blade; and drive means connected between said shaft and said pinion gears for imparting rotation to said pinion gears in opposite directions upon rotation of the ground wheels of said lawn mower.

3. In a reciprocating blade lawn mower of the type provided with a frame, ground wheels rotatably carried at either side of said frame, a shaft driven by rotation of said ground wheels and extending transversely across said frame, and a cutter blade carried in advance of said ground Wheels and arranged for transverse reciprocating movement with respect to said frame; a rack gear carried by said blade longitudinally thereof; a plurality of oppositely rotating segmental pinion gears journalled on said frame for rotation in a plane perpendicular to the plane of movement of said cutter blade and having gear teeth thereon alternately engageable with said rack gear to impart reciprocating movement to said blade; and drive means connected between said shaft and said pinion gears for imparting rotation to said pinion gears in opposite directions upon rotation of the ground wheels of said lawn mower, said lastnamed means comprising stub shafts carried by each of said pinion gears, a first set of bevel gears carried by said stub shafts, and a second set of bevel gears carried by said rst-named shaft and meshing with said rst set of bevel gears.

4. In a lawn mower; a frame, a pair of ground wheels journalled in said frame, a drive shaft extending transversely across said frame and connected to be driven upon rotatie-11 of said ground wheels, a first pair of oppositely facing bevel gears carried in longitudinally spaced relation on said shaft, a second pair of bevel gears arranged for rotation in a plane perpendicular to said first set of bevel gears and carried in meshing engagement therewith, shafts carried by each of said second pair of bevel gears, a pair of segmental pinion gears carried by said shafts and rotatable in opposite directions upon rotation of said ground wheels, a flat cutter blade arranged in advance of said frame for reciprocating movement, in a substantially horizontal plane, and a rack gear mounted on said blade in the plane of rotation of said pinion' gears and having teeth thereon to be alternately engaged by the segments of said pinion gears upon rotation thereof, whereby to impart reciprocating movement to said rack gear and said blade.

G. STARK FRAMBES.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 482,752 Prindle Sept. 20, 1892 632,173 Cameron Aug. 29, 1899 889,363 Gaefcke June 2, 1908 1,000,393 Felker Aug. 15, 1911 1,586,143 Cooper May 25, 1926 2,110,071 Pociecha Mar. 1, 1938 

